How long does a magnetic-field reversal take?
While the reversals themselves are relatively easy to delineate by examining the magnetization of rocks and sediments, the characteristics and durations of the reversal periods are more difficult to study. Sedimentary rocks and ocean-floor sediments are the preferred source of magnetic data, but deep-ocean sedimentation rates are slow, and the sedimentary interval between a period of normal and reversed magnetism is typically represented by only a few cm of sediment. Over the past couple of decades a significant amount of magnetic data have been acquired from ocean sediment cores drilled around the world, and these data have recently been compiled and examined by Florida International University geologist Brad Clement (Clement, 2004). This technique is predicated on a reliable understanding of the rates of sedimentation at the various sites, and these rates are typically determined from the reversal chronology itself, from biostratigraphic data and from isotopic data.
